We propose to investigate various aspects of reproduction in acarines of public health importance. Dermacentor variabilis will receive primary attention, but other species of ixodid and argasid ticks and mites will be studied to varying degrees depending on specific experiments. The study will involve (1) histological and histochemical analyses of growth and differentiation of reproductive systems and correlations of these parameters with nonreproductive organ systems, (2) investigations of spermatogenesis, spermiogenesis, capacitation, sperm transfer and relocation, (3) factors responsible for egg maturation and oviposition, (4) effects of hormones on development and reproduction, (5) study of aggregation, sex attraction and reproductive biology of Dermanyssus gallinae. Results from our experiments will contribute to basic understanding of reproduction and development in parasitic arthropods and help make possible larger generalizations regarding arthropod and other animal reproduction. Moreover, specific data on reproduction in acarines should allow better utilization of current control schemes and hopefully provide the data base from which improved pest control schemes might be derived.